USMLE USMLE Certifications USMLE-STEP-2 Questions & Answers

• Question 451:

  A 4-year-old child manifests symptoms of fever, sore throat, and swollen lymph nodes. The spleen tip is palpable. Throat culture and rapid slide (Monospot) test results are negative. The next logical diagnostic procedure would involve which of the following?

  A. rapid streptococcal antigen test

  B. heterophil titer

  C. Epstein-Barr virus (EBV) titer

  D. chest x-ray

  E. bone marrow examination

  Correct Answer: C

  Infectious mononucleosis may affect children of all ages. The rapid slide (Monospot) test response is positive in approximately 90% of infected persons; however, younger children with mononucleosis may have a negative result. Moreover, many younger children have poor antibody response to the heterophil titer test. The specific serodiagnostic test for EBV, the agent responsible for most cases of infectious mononucleosis, confirms the diagnosis. A repeat throat culture, even if positive for betahemolytic Streptococcus, may be of only partial value, because both infectious mononucleosis and streptococcal pharyngitis may be present simultaneously. Bone marrow examinations potentially are painful and contribute little to the correct diagnosis.

• Question 452:

  A 12-month-old patient has allergies to multiple foods. The child's mother has eliminated the foods from the diet and wants to know if these allergies will be lifelong. You tell her that some allergies do get better if the food is eliminated for 12 years. In which of the following is the allergy most likely to resolve, with elimination of the food from the diet?

  A. peanuts

  B. milk

  C. nuts

  D. fish

  E. shellfish

  Correct Answer: B

  Cow's milk allergy may occur in 23% of infants and toddlers. After elimination from the diet, by age 3, 85% no longer have symptoms on food challenge. Older children and adults may also lose sensitivity to an offending food when it is eliminated from the diet for 12 years. The exceptions are IgE-mediated allergies to peanuts, nuts, fish, or shellfish.

• Question 453:

  A beekeeper's previously healthy 6-month-old son develops gradual onset of lethargy, poor feeding, constipation, and generalized weakness. On taking a history, you determine that the child has recently been placed on a homemade formula consisting of evaporated milk, water, and honey. Which of the following is the most likely explanation for this symptom complex?

  A. sodium intoxication

  B. Hirschsprung disease

  C. hypothyroidism

  D. spinal cord tumor

  E. botulism

  Correct Answer: E

  The child described in the question seems to be afflicted with infant botulism. Clostridium botulinum spores are commonly found in honey, and the toxin responsible for the symptoms described is produced in the infant's GI tract. Therefore, children younger than 1 year should not be fed honey. Hypernatremic dehydration may show some similarities to infant botulism, but the skin and mucous membranes are characteristically dry. Serum sodium level is often greater than 160. Hirschsprung disease would explain constipation but not the other findings listed. Congenital hypothyroidism shows a more insidious onset, with prolonged constipation and weakness. In addition, developmental retardation would likely be present.

• Question 454:

  A 16-year-old girl presents with a history of primary amenorrhea. On examination, short stature and a short neck with a low posterior hairline are noted. Chromosomal analysis most likely would reveal which of the following?

  A. fragile X

  B. trisomy 18

  C. trisomy 21

  D. 45,XO

  E. XXY

  Correct Answer: D

  Turner syndrome (usually 45,XO karyotype) occurs in 1 of 3000 live births. The hallmark of this genetic disease is gonadal dysgenesis. Although sexual maturation usually does not occur, a girl with Turner syndrome occasionally will have menstrual periods but rarely will be fertile. Treatment may include estrogen replacement or growth hormone usage. Psychosocial support is extremely important.

• Question 455:

  After 10 days of nasal congestion and rhinorrhea, a 3-month-old infant develops a severe hacking cough during which he repeatedly turns dusky and appears to choke on or to vomit profuse thick, clear nasopharyngeal mucus. For 7 days, the coughing continues unabated. On physical examination, he is afebrile and his lungs are clear. His chest x-ray is normal. His WBC count is 24,000/mm3, with 15% polymorphonuclear cells, 82% lymphocytes, and 3% monocytes. Which of the following antibiotics should be used to treat this patient?

  A. amoxicillin

  B. amoxicillin-clavulanic acid

  C. erythromycin

  D. tetracycline

  E. no antibiotics are necessary

  Correct Answer: C

  Whooping cough, or pertussis, tends to have a prolonged course, with a 2-week prodrome of undifferentiated upper respiratory infection followed by approximately 2 weeks of a paroxysmal, machine gun-like cough and nasopharyngeal mucus that is strangling, thick, and clear. The typical whoop, a stridorous inspiratory gasp at the end of each paroxysm, is often absent in infants younger than 6 months. Posttussive vomiting more likely will be found in this age group. The diagnosis should be suspected in children with a paroxysmal, harsh cough and absolute lymphocytosis. Specific inquiry into the history of a severe or long-lasting cough in adult caretakers should be sought. The diagnosis is made by culture of the organism (Bordetella pertussis) or by an immunofluorescent study of throat swab material. Erythromycin is the drug of choice. It has little effect on the illness course after paroxysms are established and is used primarily to limit spread of infection to others.

• Question 456:

  A 13-year-old girl presents with parental concerns of poor posture. She has not had any back pain. On examination, she has unequal shoulder height, asymmetric flank creases, and a forward- bending test that shows rib asymmetry. The physical examination is otherwise normal. Which of the following is the most likely cause of her condition?

  A. congenital scoliosis

  B. leg length inequality

  C. idiopathic scoliosis

  D. postural roundback

  E. Scheuermann kyphosis

  Correct Answer: C

  Idiopathic scoliosis is the most common back deformity in children. The incidence peaks in early adolescence and is much more common in girls. Screening for scoliosis should be part of every well check and sports physical in children at Tanner (IIV) stages. Congenital scoliosis is caused by failure of formation or fusion of the ossific nuclei of the vertebrae. It can present at any age, depending on the degree of curvature, and is much less common than idiopathic scoliosis. Patients with leg length inequality present with a limp. Patients with Scheuermann kyphosis usually present with back pain and have a sharp kyphotic angulation with forward bending. Postural roundback is an exaggerated kyphotic appearance often seen in adolescents.

• Question 457:

  During a well-child visit, the grandmother of an 18-month-old patient is concerned because the child's feet turn inward. She first noticed this when her grandson began to walk. It does not seem to bother the child. On examining his gait, his knees point forward and his feet turn inward. Which of the following is the most likely cause of this condition?

  A. adducted great toe

  B. femoral anteversion

  C. Legg-Calv?Perthes disease

  D. medial tibial torsion

  E. metatarsus adductus

  Correct Answer: D

  Adducted great toe, metatarsus adductus, medial tibial torsion, and femoral anteversion can result in intoeing. In most cases, this is a benign condition that requires only observation. In this child, because the child's knees are straight, the rotational deformity is below this joint. In metatarsus adductus, the forefoot is adducted as compared to the hindfoot. Idiopathic avascular juvenile necrosis of the femoral head, or LeggCalv?Perthes disease, most commonly is seen in 4- to 8-year-old boys. Loss of hip medial rotation is an early sign.

• Question 458:

  A3-year-old boy suddenly begins choking and coughing while eating peanuts. On physical examination he is coughing frequently. He has inspiratory stridor and mild intercostal and suprasternal retractions. Initial management should include which of the following?

  A. back blows

  B. abdominal thrusts

  C. blind finger-sweeps of the hypopharynx

  D. permitting him to clear the foreign body by coughing

  E. emergency tracheostomy

  Correct Answer: D

  In the management of foreign body aspiration, it is generally felt that if the victim can speak, breathe, or cough, all interventions are unnecessary and potentially dangerous. When intervention is required, the first maneuver is a series of abdominal thrusts (for children >1 year of age) or back blows (for children 1 year of age or younger). When obstruction persists, foreign bodies sometimes can be removed from the oral cavity or pharynx if they can be seen, but blind finger sweeps of the hypopharynx are not recommended. Emergency tracheostomy, preferably performed by an experienced clinician, is employed only in cases of critical airway obstruction unrelieved by other maneuvers.

• Question 459:

  A 4-year-old girl presents to the emergency department with fever and a petechial rash. A sepsis workup is performed, and IV antibiotics are administered. Gram-negative diplococci are identified in the CSF. Which of the following is true of this condition?

  A. Antibiotic prophylaxis of fellow daycare attendees is not necessary.

  B. The most common neurologic residual is seizures.

  C. The presence of meningitis decreases the survival rate.

  D. Shock is the usual cause of death.

  E. Vancomycin administered intravenously is the treatment of choice.

  Correct Answer: D

  Meningococcemia is a fulminant systemic rapidly progressing infection that results in shock and is followed by death in 20% of afflicted children. The presence of meningitis has been shown to increase the survival rate to approximately 95%. Sensorineural deafness is the most common residual following bacterial meningitis. Penicillin, ampicillin, or a third-generation cephalosporin would be an appropriate antibiotic to choose for treatment. Vancomycin's spectrum of activity is limited to gram-positive organisms.

• Question 460:

  A10-year-old boy presents with a 3- to 4-day history of left ear pain. He is afebrile; he has had no symptoms of cold or cough. He has been swimming daily. On physical examination, there is pain on moving the pinna and the tragus. There is erythema and swelling of the ear canal; the tympanic membrane is obscured by thick white discharge

  Which of the following is the most likely organism involved in this case?

  A. aureus

  B. Proteus mirabilis

  C. Candida

  D. Pseudomonas aeruginosa

  E. Streptococci

  Correct Answer: D

  P. aeruginosa is the most common agent involved in external otitis. The other organisms listed may also be isolated.